This invention relates to display panels. In particular, it is an electronic circuit for a display panel that is particularly adapted to unattended military engine-generator sets.
Engine-generator sets may be used as principal sources of electrical energy in areas that are remote from power lines or they may be used as standby sources to supplement distribution systems in the case of outages. In either of these situations, it will often be desirable to have an engine generator operate unattended. Such an engine-generator set may either start and run automatically in response to an outage, or it may be started manually and left to run unattended.
A problem arises when an engine-generator set has shut down for one reason or another. Some of the reasons that might call for such a shutdown include electrical overloads, excessive voltage transients, or frequency instability. The engine may run low on fuel, overheat, lose speed control, develop low oil pressure, or the like. Whenever any of these events occurs, it is desirable to shut down the engine generator.
After a shutdown, it will be necessary to assure that the trouble or troubles that caused the shutdown have been cleared or repaired. This will normally require a visit to the site by an operator. The process of troubleshooting is facilitated by having some form of display device that indicates the existence of problems. However, it should be evident that by the time an operator arrives at a stopped engine generator there may be a number of troubles, many of which were caused by an initial trouble. Thus, a short circuit might cause the engine generator to be stopped as a result of an overload. Once the engine generator has stopped, its terminal voltage will go to zero, its frequency will go to zero, the oil pressure in the engine will go to zero, and there may be other associated trouble indications. It is desirable to have a means of notifying the operator which trouble came first and to suppress indications of what came later. This will enable the operator to clear the first trouble and attempt to restore the engine generator to operation. If the system has additional troubles when he does this, his attention should be called to the next disabling trouble. This will enable the operator to clear troubles in sequence until the system is restored to operation.
When an engine generator is designed for military use, an additional factor must be taken into consideration. This is the necessity of rendering the system resistant to various forms of radiation and to electromagnetic interference. This is also referred to as hardening. The circuit for control of status displays in a remote engine generator must exhibit an appropriate amount of resistance to prompt gamma rays, which is an extremely dense burst over a period of the order of tens or hundreds of nanoseconds. The circuit must be resistant to a given total dose of gamma radiation. It must withstand a given flux of neutrons. It must not be affected by alpha and beta particles. Finally, it must withstand exposure to a certain level of electromagnetic pulses.